examples/src/main/java/org/apache/spark/examples/ml/JavaVectorSlicerExample.java
<reponame>LexCC/spark-py/*
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 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
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 * distributed under the License is distributed on an "AS IS" BASIS,
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package org.apache.spark.examples.ml;

import org.apache.spark.sql.SparkSession;

// $example on$
import java.util.Arrays;
import java.util.List;

import org.apache.spark.ml.attribute.Attribute;
import org.apache.spark.ml.attribute.AttributeGroup;
import org.apache.spark.ml.attribute.NumericAttribute;
import org.apache.spark.ml.feature.VectorSlicer;
import org.apache.spark.ml.linalg.Vectors;
import org.apache.spark.sql.Dataset;
import org.apache.spark.sql.Row;
import org.apache.spark.sql.RowFactory;
import org.apache.spark.sql.types.*;
// $example off$

public class JavaVectorSlicerExample {
  public static void main(String[] args) {
    SparkSession spark = SparkSession
      .builder()
      .appName("JavaVectorSlicerExample")
      .getOrCreate();

    // $example on$
    Attribute[] attrs = {
      NumericAttribute.defaultAttr().withName("f1"),
      NumericAttribute.defaultAttr().withName("f2"),
      NumericAttribute.defaultAttr().withName("f3")
    };
    AttributeGroup group = new AttributeGroup("userFeatures", attrs);

    List<Row> data = Arrays.asList(
      RowFactory.create(Vectors.sparse(3, new int[]{0, 1}, new double[]{-2.0, 2.3})),
      RowFactory.create(Vectors.dense(-2.0, 2.3, 0.0))
    );

    Dataset<Row> dataset =
      spark.createDataFrame(data, (new StructType()).add(group.toStructField()));

    VectorSlicer vectorSlicer = new VectorSlicer()
      .setInputCol("userFeatures").setOutputCol("features");

    vectorSlicer.setIndices(new int[]{1}).setNames(new String[]{"f3"});
    // or slicer.setIndices(new int[]{1, 2}), or slicer.setNames(new String[]{"f2", "f3"})

    Dataset<Row> output = vectorSlicer.transform(dataset);
    output.show(false);
    // $example off$

    spark.stop();
  }
}

